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KVM: riscv: Use an rwlock for mmu_lock

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RISC-V KVM currently uses a spinlock for mmu_lock. That serializes all
G-stage MMU operations, including permission-only updates that do not
allocate or free page-table pages.

Use KVM's rwlock form of mmu_lock, as x86 and arm64 already do. Keep the
existing map, unmap and teardown paths on the write side. This prepares
RISC-V for read-side handling of G-stage permission updates.

Signed-off-by: Jinyu Tang <tjytimi@163.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260517153427.94889-3-tjytimi@163.com
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Jinyu Tang 2026-05-17 23:34:24 +08:00 committed by Anup Patel
parent 9090ba2e7c
commit cc98f006c6
3 changed files with 15 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/riscv/include/asm/kvm_host.h
View File

@ -48,6 +48,8 @@
#define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE
#define KVM_HAVE_MMU_RWLOCK
#define KVM_DIRTY_LOG_MANUAL_CAPS (KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE | \
KVM_DIRTY_LOG_INITIALLY_SET)

2
arch/riscv/kvm/gstage.c
View File

@ -414,7 +414,7 @@ bool kvm_riscv_gstage_unmap_range(struct kvm_gstage *gstage,
* to prevent starvation and lockup detector warnings.
*/
if (!(gstage->flags & KVM_GSTAGE_FLAGS_LOCAL) && may_block && addr < end)
cond_resched_lock(&gstage->kvm->mmu_lock);
cond_resched_rwlock_write(&gstage->kvm->mmu_lock);
}
return flush;

24
arch/riscv/kvm/mmu.c
View File

@ -27,9 +27,9 @@ static void mmu_wp_memory_region(struct kvm *kvm, int slot)
kvm_riscv_gstage_init(&gstage, kvm);
spin_lock(&kvm->mmu_lock);
write_lock(&kvm->mmu_lock);
flush = kvm_riscv_gstage_wp_range(&gstage, start, end);
spin_unlock(&kvm->mmu_lock);
write_unlock(&kvm->mmu_lock);
if (flush)
kvm_flush_remote_tlbs_memslot(kvm, memslot);
}
@ -67,9 +67,9 @@ int kvm_riscv_mmu_ioremap(struct kvm *kvm, gpa_t gpa, phys_addr_t hpa,
if (ret)
goto out;
spin_lock(&kvm->mmu_lock);
write_lock(&kvm->mmu_lock);
ret = kvm_riscv_gstage_set_pte(&gstage, &pcache, &map);
spin_unlock(&kvm->mmu_lock);
write_unlock(&kvm->mmu_lock);
if (ret)
goto out;
@ -88,9 +88,9 @@ void kvm_riscv_mmu_iounmap(struct kvm *kvm, gpa_t gpa, unsigned long size)
kvm_riscv_gstage_init(&gstage, kvm);
spin_lock(&kvm->mmu_lock);
write_lock(&kvm->mmu_lock);
flush = kvm_riscv_gstage_unmap_range(&gstage, gpa, size, false);
spin_unlock(&kvm->mmu_lock);
write_unlock(&kvm->mmu_lock);
if (flush)
kvm_flush_remote_tlbs_range(kvm, gpa >> PAGE_SHIFT,
@ -143,9 +143,9 @@ void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
kvm_riscv_gstage_init(&gstage, kvm);
spin_lock(&kvm->mmu_lock);
write_lock(&kvm->mmu_lock);
flush = kvm_riscv_gstage_unmap_range(&gstage, gpa, size, false);
spin_unlock(&kvm->mmu_lock);
write_unlock(&kvm->mmu_lock);
if (flush)
kvm_flush_remote_tlbs_range(kvm, gpa >> PAGE_SHIFT,
size >> PAGE_SHIFT);
@ -523,7 +523,7 @@ int kvm_riscv_mmu_map(struct kvm_vcpu *vcpu, struct kvm_memory_slot *memslot,
if (logging && !is_write)
writable = false;
spin_lock(&kvm->mmu_lock);
write_lock(&kvm->mmu_lock);
if (mmu_invalidate_retry(kvm, mmu_seq))
goto out_unlock;
@ -546,7 +546,7 @@ int kvm_riscv_mmu_map(struct kvm_vcpu *vcpu, struct kvm_memory_slot *memslot,
out_unlock:
kvm_release_faultin_page(kvm, page, ret && ret != -EEXIST, writable);
spin_unlock(&kvm->mmu_lock);
write_unlock(&kvm->mmu_lock);
return ret;
}
@ -576,7 +576,7 @@ void kvm_riscv_mmu_free_pgd(struct kvm *kvm)
void *pgd = NULL;
bool flush = false;
spin_lock(&kvm->mmu_lock);
write_lock(&kvm->mmu_lock);
if (kvm->arch.pgd) {
kvm_riscv_gstage_init(&gstage, kvm);
flush = kvm_riscv_gstage_unmap_range(&gstage, 0UL,
@ -586,7 +586,7 @@ void kvm_riscv_mmu_free_pgd(struct kvm *kvm)
kvm->arch.pgd_phys = 0;
kvm->arch.pgd_levels = 0;
}
spin_unlock(&kvm->mmu_lock);
write_unlock(&kvm->mmu_lock);
if (flush)
kvm_flush_remote_tlbs(kvm);